This multicenter phase II study will be a randomized, double-blind and open-label, placebo-controlled, dose-ranging clinical trial to determine the safety and efficacy of chronically administered MDL 28,574A in HIV- positive patients. The study will contain five treatment arms of asymptomatic or mildly symptomatic HIV-positive patients with demonstrated CD4 cell deficiency in the peripheral blood compartment and the duration of treatment with study drug will be 24 weeks. Patients will be randomized to one of 5 double-blind treatment groups to maintain heterogeneity within the study arms. Four treatment groups will receive active MDL 28,574A and the fifth treatment group will receive MDL-28,574A-matched placebo as monotherapy during the initial 12 weeks of treatment.